Estimating the number of clear sky nights using GOES-16 images: a search for astronomical sites in Colombia

摘要

Data from the Geostationary Operational Environmental Satellite 16 (GOES-16) are used to study the number of clear nights over Colombia in order to identify potential sites for astronomical observations. First, we compare data from the Advanced Baseline Imager (ABI) with in-situ observations from an all-sky camera in order to validate the cloud cover information from the ABI retrievals. Then, we extend the analysis of the GOES-16 cloud cover fields to quantify the number of hours with low values of cloud cover for each pixel and each day of 2018 for a region that includes Colombia. A clear night is defined as one with five or more consecutive hours with a low fraction of cloud cover. We select the potential sites as those with more than 80 clear nights and with an altitude higher than 2000 m above sea level (m.a.s.l.). Our analyses showed that nine sites fulfil these conditions: five are in Colombia, three are in Ecuador and one in Venezuela. From our sample, eight out of the nine sites are in the Andes Mountains. The results suggest that the most suitable site for astronomical observations in Colombia is located near to Laguna de la Cocha, in the department of Narino, with 135 clear nights in 2018 (about 37% of the year), followed by a site near to Lago de Tota, with 117 clear nights (about 32% of the year), located near the centre of the country. Exploration of regions outside Colombia showed that the Ecuadorian Andes has locations with approximately 48% of clear nights during the studied year. We conclude that the use of GOES images to measure the number of clear nights in order to select potential astronomical site locations has a great potential.